[nextaccountic]

I would love to see TST integrated in Firefox

TST (or one of its plugins) may become buggy and a memory hog if you have too many tabs. Things like dragging tabs stop working if you have too many tabs opened at once

I just wish that, when they integrate a subset of functionality of TST, further extensions can customize its behavior (like currently extensions can customize TST adding new functionality)

[lproven]

JFWIW it is now in Waterfox... kinda.

https://www.waterfox.net/blog/waterfox-x-treestyletab/

[Tarq0n]

If you just want a vertical tab list, Vertical Tabs Reloaded stays performant up to thousands of tabs for me.